1. Field of the Invention
The present invention relates generally to a wire rope termination connector, and in particular to a wire rope termination connector for terminating a core wire rope in a coaxial cable, such as a minesweeping magnetic influence cable, where the core wire rope is a strength member that is subject to corrosion, including salt water, such as seawater, conducting a current. The invented termination connector is resistant to corrosion, typically environmentally isolates the strength member, typically electrically insulating, and adaptable for a variety of modular fittings that include metal such as stainless steel and polymeric materials such as engineering plastics.
2. Prior Art
There are many types of termination connectors for wire rope, where almost all termination connectors are metallic, usually steel. Those connectors having good corrosion resistance are stainless steel spelter sockets, which typically use zinc, in part because zinc has a more negative electrochemical potential than steel, and it has a lower melting point.
The art teaches that the process of forming a zinc spelter socket includes that the socket be filled with molten zinc. The melting point for zinc is around 790° F. The process includes applying a tight wire serving band at the point where the socket base will be. The individual strands of the wire rope are unwound, straightened, and evenly spread so that they form an included angle of approximately 60 degrees. The angle has to be sufficiently wide that individual strands can be properly accessed as they are cleaned.
A fibrous core is cut out and positioned as close to the serving band as possible prior to cleaning the strands. The strands are typically cleaned with a chlorinated solvent such as 1-1-1 trichloroethane, perchloroethane, and perchloroethylene. These solvents are used because they cut grease, but more importantly they are not flammable and dry quickly. A muriatic acid wash is also recommended. Muriatic acid is the common name for hydrochloric acid. The wash typically causes the acid to fume. The acid is neutralized in a solution of bicarbonate, giving off carbon dioxide and sodium chloride.
The rope is then dipped in a flux of zinc-ammonium chloride flux heated to 200° F. The flux is used to remove oxide films, promote wetting, and prevent re-oxidation of the surfaces during heating. The strands of wires are then pointed downward until the wires have dried thoroughly. The wires are compressed in a clamp/vise, a tight bundle which will permit the wires to be slipped into the socket. Before threading, the entire socket is heated to dispel any residual moisture and will also prevent the zinc from freezing or cooling prematurely. The heating also expands the entrance of the socket.
The socket should never be heated after the rope has been slid into the socket, as the heat may cause damage to the rope. Warm the socket, and then thread the rope into the socket. The strands of wire are distributed evenly in the socket basket so the molten zinc can surround each wire. Extreme care is used to align the rope in the center of the socket. Next the socket base is sealed with fire clay or putty. The seal material should not penetrate into the socket base. If the seal material does penetrate it could prevent the zinc from penetrating the full length of the socket basket, thereby creating a void that would collect moisture after the socket is placed in service.
The zinc has to be poured at a temperature of 950° F. to 1000° F. (well below the boiling point of 1665° F.). Another word of caution is that overheating of the zinc may affect its bonding properties. The pouring of the zinc is in one continuous stream until it reaches the top of the basket and all wire ends are covered. After the zinc, cable and socket have cooled to a point where they can be easily handled, the serving band is removed from the socket base. It is good practice to lubricate the rope. Wire rope lubricant is applied to the rope at the base of the socket.
Spelter sockets with zinc have several problems, especially for forming a termination connector on a magnetic influence minesweeper cable. One challenge is that conventional spelter sockets are conductive, and don't lend themselves to large wire ropes, which have a very high heat capacity, and therefore the zinc will cool quickly resulting in a weak bond. In use, electric current flows through the magnetic influence cable, and the conductive socket potentially can drain off some of the cable's current and drain current from the ambient electrified salt water. Also, from the prior art discussion one can understand that the process of forming a zinc spelter socket does not lend itself to shipboard repairs.